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Abstract

Light-driven ion (proton) transport is a crucial process both for photosynthesis of green plants and solar energy harvesting of some archaea. Here, we describe that TiO₂/C₃N₄ semiconductor heterojunction nanotube membrane can realize a similar light-driven directional ion transport performance as biological systems. This heterojunction system can be fabricated by two simple deposition steps. Under unilateral illumination, TiO₂/C₃N₄ heterojunction nanotube membrane can generate a photocurrent of about 9 μA/cm², corresponding to a pumping stream of ∼5500 ions per second per nanotube. By changing the position of TiO₂ and C₃N₄, a reverse equivalent ionic current can also be realized. Directional transport of photo generated electrons and holes results in a transmembrane potential, which is the basis of the light-driven ion transport phenomenon. As a proof of concept, we also show that this system can be used for enhanced osmotic energy generation. The artificial light-driven ion transport system proposed here offers a further step forward on the roadmap for the development of ionic photoelectric conversion and their integration in other applications, e.g. water desalination.